Why mosquitoes are becoming harder to beat

Vector Control The fight to eradicate malaria may have saved the lives of three million children since the turn of the century but progress is stalled because mosquitos are becoming resistant to pesticides.

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According to the World Malaria Report, all the major malaria-carrying Anopheles mosquito species have developed resistance to all four existing types of insecticide, and resistance is spreading - it has been detected in 64 countries. Lack of detailed information on resistance is hampering progress on eradication, according to the World Health Organisation (WHO), because most of the affected countries have yet to implement testing of the efficacy of insecticides against local mosquito species.

"The situation is critical — we have reached the tipping point," says one of the leading experts in vector control, Dr Nick Hamon CEO of the public health development charity IVCC. "The WHO estimates that if current trends continue resistance to insecticides will lead to additional deaths of about 125,000 per year, mostly children under five years old. No new public health insecticide has been developed in over 30 years."

Distributing bed nets treated with insecticide and spraying inside homes has been mainly responsible for the success of the current campaign against malaria, but the rapid spread of resistance means these measures will soon be only partially effective.

Scientists at IVCC have developed a new approach that attacks mosquitos in several different ways so they cannot develop resistance.

"The new system uses three insecticides, each with a different mode of action that kills mosquitos in a different way," Dr Hamon says. "This makes it very hard for the mosquitoes to develop resistance if the insecticides are managed together – something we call integrated vector control."

Based in the School of Tropical Medicine at Liverpool University, IVCC was set up in 2005 as a product development partnership to bring together leading scientists and agrochemical companies to design new insecticides.

Dr Hamon is now appealing for funding to develop the new insecticide system, which is likely to cost more than $100m. "Malaria is especially important because it has a devastating economic effect on developing economies. It is no coincidence that malaria-endemic countries are amongst the poorest in the world," Dr Hamon says.